A scientist with samples of animal cells infected with the Zika virus(Credit: Huy Mach)

Since the World Health Organization declared the Zika virus disease a global public health emergency in February, researchers have been working at full speed to develop a vaccine for it. Multiple experimental vaccines are in the works, as are solutions to eliminate the Aedes aegypti, from using old tires as traps to releasing genetically engineered mosquitoes. While the world waits for the announcement of a cure, scientists have discovered a human antibody that can protect developing fetuses, probably the number one victim of the disease.

Microcephaly, the development of abnormally small heads in fetuses, is the most well-known birth defect inflicted by the Zika virus but not the only one. Others include missing brain tissue and deformed limbs. According to health officials from the Centers for Disease Control and Prevention, the first trimester is the period of greatest risk for pregnant women and given this fact, it makes sense to develop a treatment that can counter the virus during this crucial stage.

By screening blood samples from those who have been infected with the virus, researchers at Washington University School of Medicine in St. Louis and Vanderbilt University School of Medicine found an antibody, called ZIKV-117, which appeared to be particularly effective at neutralizing Zika strains. When given to pregnant mice either a day before or after they were infected with the virus, they found that it significantly reduced the amount of damage inflicted by the virus on the females, fetuses and placenta, compared with those that did not get the antibody.

"We did not see any damage to the fetal blood vessels, thinning of the placenta or any growth restriction in the fetuses of the antibody-treated mice," said co-author Indira Mysorekar from Washington University, adding that the anti-Zika antibodies were able to keep the fetus safe from harm by blocking the virus from crossing the placenta.

The results of this study are significant in that ZIKV-117 is the first antiviral that has been shown to work in pregnancy to protect developing fetuses from the Zika virus, said co-senior author on the study, Michael Diamond. "This is proof of principle that Zika virus during pregnancy is treatable, and we already have a human antibody that treats it, at least in mice," he added.

The researchers also tested the antibody in adult male mice against a lethal dose of the virus to see how effective it would be under the most stringent conditions. The good news is that ZIKV-117 worked – keeping the mice alive even when it was given five days after infection.

While further work will have to be conducted before the antibody can be tested on humans, this study suggests a number of things. First, that even in the absence of a human vaccine, antibodies can be used to protect adults and fetuses from the virus, which means that pregnant women living in Zika zones can receive them throughout their pregnancies as a safeguard regardless of whether they have been infected. Secondly, there is a possibility antibodies might be used to treat those who have been diagnosed with the disease.

At present, researchers are working to develop the antibody as a potential therapy for humans as well as a cure for infections caused by the disease. "We know that Zika can persist in certain parts of the body, such as the eyes and the testes, where it can cause long-term damage, at least in mice," said Diamond. "Now we want to know whether it can clear persistent infection from those parts of the body."